Antenna system



Dec, 23, 1941. P. JAKEL 2,266,868

ANTENNA SYSTEM Filed June 29, 1940 2 Sheets-Sheet 1 SIGN/4L INTENSITY Z Vc' I 5 2 ,5 a XZII/IiI PX?! M a P7 2 3nventor PAUL IA/(EL TF/INSM/TTEE Dec. 23, 1941. I P. JAKEL 2,266,868

ANTENNA SYSTEM I Filed June 29, 1940 2 Sheets-Sheet 2 3nventor 'PAUL JA/Q L kggw Gttorneg Patented Dec. 23, 1941 ii STTES ANTENNA SYSTEM poration of Germany Application June 29, 1940, Serial No. 343,083 In Germany February 17, 1939 8 Claims.

The present invention is concerned with an arrangement adapted to adjust or regulate the phase and amplitude relations of antenna currents of antenna arrays which, by the coaction of several differently fed radiators result in adirectional characteristic of a definite shape or pattern.

It is known in the art to obtain directive diagrams or radiation diagrams by the combined action of several directional or non-directional radiators which are fed with radio frequency energy of dissimilar phase and/or amplitude froma joint transmitter. The various radiations are superposed in space with the result that they will either reinforce or weaken one another with the consequence that intensified directive effects or extinction or silence zones are secured.

Now, if the use of of such radiators the direction of maximum radiation intensity or a zone of silence is to be produced with great precision and, more particularly, if in such regions of silence (dead zones) the several radiations are to offset completely, it is necessary to have available ways and means so that the phase and amplitude re' lations of the various radiations may be accurately adjusted and regulated. Now, it has been suggested in the earlier art to insure phase regulation between the antenna currents by including phase adjusting setting or regulating means in the energy feeder lines of the various antennae at a point above the branch-off from the joint antenna lead. What has been used for this purpose, for instance, are variable impedances or by-pass leads the length thereof being adjustable by a short-circuit bridge which is shiftable trombone-fashion or like a telescope.

However, one difficulty and drawback that has been met in the practical application of such schemes is that in the attempt to change the phase between the antenna currents of the various radiators there would invariably be occasioned also a change in the amplitude relations, and vice versa, and this precluded all chances to effect satisfactory regulation.

Now, this shortcoming is obviated by the invention. By examining the problem and object from a mathematical angle instructions have been ascertained as to how a tap line must be associated with the antenna feeder line if phase or amplitude regulation is to be insured without an incidental effect upon the amplitude and the phase, respectively.

For a more detailed explanation of the problem and object of the invention a directive or beam transmitter is shown in Figure I, while Figure 2 shows the resultant radiation diagram shown in Cartesian co-ordinates in Figure 2, this diagram presenting a minimum in the direction normal to the plane of the sheet antenna;

7 Figure 3 shows an equivalent diagram of the present invention; Figure 4 shows a diagram use-- ful in calculatingv values for producing the invention and Figure 5' shows an embodiment of the present invention. Figure 1 shows two radiator systems 81 and S2. These two radiator systems are fed from a joint and common transmitter S by way of the energy feeder lead a, the two feeder leads s1 and 52 being branched off therefrom at point A to supply the two systems. The

two leads s1 and s2 are of equal electrical characteristics, but lead s2 is transported with the result that the two halves'of the beam transmitter are fed with equal, but opposite currents, that is, currents presenting a phase displacement angle of degrees.

However, in spite of extremely great symmetry in the mechanical mounting, it is unavoidable that slight disparities in the feed of the two antenna halves occur in practice. The consequence is that the phase relations will not be exactly 180 degrees or that the amplitudes of the feed currents are alike. This situation translates itself in the directional diagram insofar as the minimum is not exactly in the zero position or that it does'no't occur in the median perpendicular line of the radiator. If each half of the antenna itself has a directional diagram, then, in the presence of faulty phase position, there arises in addition an inequality in the intensity of the two main radiations,

For a satisfactory adjustment of the directional diagram, it is therefore necessary to provide ways and means adapted to adjust the amplitude relations of the currents in the two radiator halves and their phase relations independently of each other.

Now, such i e-adjustment is feasible according to the invention in a very simple and precise manner by the aid of a tap line in one or in both radiator halves, with close observation of the mathematical rules hereinbelow laid down.

The assumption shall be made that the dipole group which constitutes the left-hand or righthand half of the radiator at its feeding point B and C, respectively, involves a purely ohmic input impedance (resistance) equal to the surge impedance Z of the feeder line. In this case the equivalent diagram Figure 3 may beused. The tap line has a length an, and its base D is at a distance from the branch-off A of the antenna feeder lines equal to :01. The potential acting at A shall be designated by VA. The potential acting at B is then expressible by the equation The input impedance of the short-circuited tap line T is:

:62 being the length of tap line T. Hence, the resultant input impedance at the connecting point D of the tap line turns out to be:

RD =jZ sin f 7 5 from the paralleling of Z and a'Z tan 2. Neglect-- ing line drop the input impedance of the righthand half of the beam is R cos +jZ sin where x1 being the distance from the source to the tap line T, so that at the branch-off point A a current amounting to flows into the right-hand half of the beam. The feeder potential at point C is Introducing the values derived for IE and Ic, then the following equations result for the quotients The two formulae derived for may be interpreted in the following manner: 1) For 1=constant a straight line results directly from Equation 1 which passes through point 1. For different values of 01 there thus results a family of straight lines, the angle of inclination of each of the latter being given by tan =tan -1). (2) For constant 2 a circle results from Equation 2 the center of which is at point (1-1' A2 cot 2), while the radius thereof has this value /2.cot 2. For diiferent values of z there thus results a family of circles, the center of all of the latter being located on a perpendicular on the real axis passed through point 1. The real axis at the same time is a tangent for all of these circles. What the equations also bring out is the fact that the circle diagrams periodically recur for changes in the parameters by 1r.M2

Figure 4 shows the values of in the complex plane in parametric dependence upon 51 (family of straight lines through point 1) and upon z (family of circles through point 1).

It will thus be seen that by the aid of a tap line at small distance from the branch-off point A of the feeder leads (say, about r1=.025 by variations of its length an amount equal to M4 approximately, it is possible to vary the ratio within wide limits, without a change in the phase relations of the two currents being incidentally caused. The quotient of the two factors of the antenna currents, using the circle diagram representation, shifts along the periphery of a large circle (Figure 4) which in the neighborhood of unity may be replaced by a straight line.

On the other hand, phase adjustment without disturbing the amplitude relations is possible by providing a tap line at a distance of M4 from the branch-off point A. In this case the value of the current quotient moves along a line parallel to the imaginary axis so that in the presence of slight phase differences no change in the amplitude will happen.

In the light of these deductions and considerations, it is suggested by the invention, with a view to regulating or adjusting the amplitude and/or phase relations of the antenna currents in the radiators of a radiator array jointly fed from a transmitter, said beam or radiator array having a directive characteristic or diagram of prearranged shape as a result of the coaction of the fields of the said radiators, to provide one or several variable impedances, preferably tap lines of variable length in the feeder line or lines of one or more radiators for the adjustment of the amplitude relation, roughly at a distance of .05 \+n.M2 from the branch-off point of the radiator feeder leads and/or for phase adjustment one or more tap lines at a distance of roughly M4+n.M2 from the said branch-off point, n being any integral number.

An exemplified embodiment of this basic idea of the invention is illustrated in Figure 5. At a distance equal to M4 from the branch-off of the two feeder leads s1 and s2 is provided a tap line x2 for phase adjustment, while in the feeder lead of the opposite radiator arrangement 82 is provided a tap line x2 for amplitude adjustment. The length of these two tap lines may be varied by the aid of the telescoping slides P1 and P2, respectively.

What may also be inferred from the circle diagrams Figure 4 is, however, that any desired amplitude relation of the current, with any desired phase relation, could also be regulated by the aid of a single tap line. To this end, the distance of the base of this tap line from the branch-off point of the feeder lines and the length of the tap line must be variable. The size of these quantities required for any given relations can be directly read in the graph sheet so that both the phase and the amplitude balancing are predeterminable; hence, there is no need to ascertain what has to be done empirically or tentatively.

I claim:

1. An arrangement for independently and selectively adjusting the phase and amplitude relations of antenna currents of the radiators of an antenna array, said radiators being connected together by an energy feed line, said feed line being energized from a source of high frequency energy, said arrangement comprising a plurality of variable reactances connected in shunt to said feed line, one of said variable reactances being so spaced from said source that a variation of its reactance varies the amplitude of the current in said radiators beyond its point of connection without a variation in phase while another of said reactances is so spaced from said source that a variation of its reactance varies the phase of the current in said radiators beyond its point of connection without a variation in amplitude.

2. An arrangement for independently and selectively adjusting the phase and amplitude relations of antenna currents of the radiators of an antenna array, said radiators being connected together by an energy feed line, said feed line being energized from a source of high frequency energy, said arrangement comprising a plurality of variable length tap lines, one of said lines being so spaced from said source that a variation of its length varies the amplitude of the current in said radiators beyond its point of connection Without a variation in phase while another of said tap lines is so spaced from said source that a variation of its length varies the phase of the current in said radiators beyond its point of connection without a variation in amplitude.

3. An arrangement for independently and selectively adjusting the phase and amplitude relations of antenna currents of the radiators of an antenna array, said radiators being connected together by an energy feed line, said feed line being energized from a source of high frequency energy, said arrangement comprising a plurality of variable reactances connected in shunt to said feed line, one of said variable reactances being spaced a distance of .05A+nA/2 from said source so that a variation of its reactance varies the amplitude of the current in said radiators beyond its point of connection Without a variation in phase while another of said reactances being spaced from said source a distance of A/4+nA/2 so that a variation of its reactance varies the phase of the current in said radiators beyond its point of connection without a variation in amplitude, A being the operating wavelength and n any integer.

4. An arrangement for independently and selectively adjusting the phase and amplitude relations of antenna currents of the radiators of an antenna array, said radiators being connected together by an energy feed line, said feed line being energized from a source of high frequency energy, said arrangement comprising a plurality of variable length tap lines connected in shunt to said feed line, one of said tap lines being spaced a distance of .05A+nA/2 from said source so that a variation of its length varies the amplitude of the current in said radiators beyond its point of connection without a variation in phase while another of said tap lines is spaced from said source a distance of A/4+nA/2 so that a variation of its length varies the phase of the current in said radiators beyond its point of connection without a variation in amplitude, A being the operating Wavelength and n any integer.

5. In combination with a high frequency energy source, a load and an energy line connecting said source and said load, of a variable reactance connected across said line at such distance from said energy source that the phase of energy applied to said load may be varied without affecting the amplitude thereof and a second variable reactance connected across said line at such distance from said energy source that the amplitude of energy applied to said load may be varied Without affecting the amplitude thereof.

6. In combination with a high frequency energy source, a load and an energy line connecting said source and said load, of a variable length tap line connected across said line at a distance from said energy source so that the phase of energy applied to said load may be varied without affecting the amplitude thereof and a second variable length tap line connected across said line at a distance from said energy source that the amplitude of energy applied to said load may be varied without aifecting the amplitude thereof.

'7. In combination with a high frequency energy source, a load and an energy line connecting said source and said load, of a variable reactance connected across said line at a distance of .05A+'nA/2 from said energy source so that the phase of energy applied to said load may be varied without affecting the amplitude thereof and a second variable reactance connected across said line at such distance from said energy source that the amplitude of energy applied to said load may be varied without affecting the amplitude thereof, A being the operating wavelength and n any integer.

8. In combination with a high frequency energy source, a load and an energy line connecting said source and said line connecting said source and said load of a variable length tap line connected across said line at a distance of .05A+nA/2 from said energy source so that the phase of energy applied to said load may be varied without afiecting the amplitude thereof and a second variable length tap line connected across said line at a distance of A/4+nA/2 from said energy source so that the amplitude of energy applied to said load may be varied without affecting the amplitude thereof, A being the operating wavelength and 'n any integer.

PAUL JAKEL. 

